The prison population in England and Wales has hit a record high of 86,654 following the courts' decision to remand hundreds charged with rioting and looting in custody.

The Ministry of Justice said the prison population had risen by 723 over the past week. Officials are making contingency plans to accelerate the opening of new prison buildings and bring mothballed accommodation back into use.

There are currently only 1,439 spare useable places left in the jail system, but prison chiefs say they remain confident they have enough to cope with those being imprisoned by the courts in relation to the recent riots.

"We are developing contingencies to increase useable capacity should further pressure be placed on the prison estate," a Prison Service spokesperson said.

It is thought the plans include opening accommodation at the new Isis prison next to Belmarsh in south-east London earlier than expected, and bringing back into use a wing at Lewes prison, East Sussex, which had been closed for refurbishment, back into use.

The Prison Service said that it had no plans to reverse the decision to close two prisons - Latchmere House in London, and Brockhill in Redditch - next month.

"We are managing an unprecedented situation and all the staff involved should be commended for their dedication and hard work during this difficult time," said a Prison Service spokesperson. "We currently have enough prison places for those being remanded and sentenced to custody as a result of public disorder."

The use of emergency police cells known as Operation Safeguard is the normal safety valve when the Prison Service is running out of space, but this is not currently a possibility as police forces need to keep holding capacity on standby to deal with further possible disturbances. The pressure is particularly acute in London, where inmates are being moved out of the capital to other institutions in order to free up space.

Geoff Dobson, the deputy director of the Prison Reform Trust, said the rapid increase in prison numbers meant that some parts of the system were "becoming human warehouses, doing little more than banging people up in overcrowded conditions, with regimes that are hard pressed to offer any employment or education. The likelihood is that for some first time offenders that will provide a fast-track to a criminal career."

His concerns were shared by Paul McDowell, the chief executive of Nacro, the crime reduction charity, and former governor of Brixton prison, who also warned that rehabilitation work to tackle reoffending would simply go by the board as jails tried to cope with the rapid rise in prisoner numbers.

Labour's prison spokesperson, Helen Goodman, said she was becoming increasingly concerned about the remaining capacity. "The violence that was seen on the streets of Britain last week must be punished, but the Tory-led government also have a responsibility to ensure that the sentences handed down are being served safely," she said.

"Since May last year this Tory-led government has scrapped the prison building programme and closed four prisons, which has reduced prison capacity even further.

"The prison population has reached a record high and prison and probation officers are being increasingly overstretched. It is vital for public safety and for security in our prisons and the youth secure estate that prison and probation staff get the resources and support they need," she said.